The Studies of the Causes and Effects of Smoking Cessation will be carried out at the Jerry L. Pettis Memorial VA Medical Center in Loma Linda, California in collaboration with Dr. Linda H. Ferry MD, MPH. As a supplement to an ongoing VA protocol, ambulatory veterans from the VA Preventive Medicine Clinic and the VA Stop Smoking Classes will be recruited to participate in this two pronged pilot study to test whether immunoglobulin levels change after smoking cessation and to evaluate possible hereditary influences on smoking behaviors. Personal histories of smoking and biological samples (blood from each recruited patient) will be provided to the MEDIB laboratory for molecular analyses. MEDIB will evaluate the differences between subjects that do versus those that do not succeed in quitting smoking. The study population will consist of approximately 300 (male and female) ambulatory veterans who are enrolled in the ongoing Smoking Cessation Program.